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GI System > Pharmacological basis for treatment of GI disorders > Flashcards

Pharmacological basis for treatment of GI disorders Flashcards

1
Q

Give some H2 Receptor Antagonists.

A

Cimetidine
Ranitidine
Famotidine
Nizatidine

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2
Q

How do H2 receptor antagonists work?

A

Inhibit histamine, Ach and gastrin stimulated acid secretion from parietal cells by blocking H2 receptor

also promote healing of duodenal ulcers, but stopping treatment causes relapse

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3
Q

Which H2-receptor antagonist can cause gynecomastia?

A

Cimetidine

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4
Q

Which H2 antagonist inhibits P450 enzymes?

A

Cimetidine inhibits P450 enzymes, decreasing number of drugs metabolised by these enzymes.

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5
Q

Give someProton Pump Inhibitors (PPIs).

A

Omeprazole, Lanzoprazole, Pantoprazole, Rabeprazole

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6
Q

How do PPIs work?

A

Irreversible inhibit the H+/K+ ATPase in parietal cells, inhibiting gastric acid secretion

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7
Q

What is the function of PGE2 and PGI2?

A

gastro protective

inhibit gastric acid secretion and stimulate mucus and bicarbonate secretion, providing protection

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8
Q

What is the function of Misoprolol?

A

stable analogue of PGE1

  • inhibits gastric acid secretion
  • inhibits activity of parietal cells
  • increases mucosal blood flow and can increase secretion of bicarbonate and mucus
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9
Q

What is thCaution of misoprolol?

A

induces labour and abortion

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10
Q

What is the effect of Dopamine on gut motility and emptying?

A

Relaxes gut by activating D2 receptors in LOS and stomach (fundus and antrum)

also inhibits release of Ach from myenteric neurones, preventing contraction of gut smooth muscle (inhibits gastric motility and emptying)

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11
Q

Give an example of a D2 Receptor Antagonist.

A

Metoclopramide

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12
Q

What is the effect of Metoclopramide on gastric motility and emptying?

A

Increases gastric motility by inhibiting presynaptic and postsynaptic D2 receptors and inhibits 5-HT3 receptors in CNS, increasing gastric motility and also acting as an antiemetic

prokinetic effects are stimulating 5-HT4 receptors in ENS, increasing Ach release from myenteric neurones, increasing LOS and gastric tone, increasing intragastric pressure and accelerating emptying (relaxes pyloric sphincter)

also stimulates inhibitory nitrenergic neurones mediating NO release

*all reduces likelihood of reflux

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13
Q

Give some examples of Anti-spasmodic agents.

A

propantheline
diclocxerine (dycyclomine)
mebeverine

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14
Q

How do anti-spasmodic drugs work?

A

Reduce muscle spasms in the bowel and relax smooth muscle in the GIT

useful in IBS and diverticular diseases

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15
Q

What is the role of Muscarinic receptor antagonists during spasms?

A

Inhibit parasympathetic activity, reducing spasms in the bowel

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16
Q

What is the function of Pharmacological Intervention in gastric ulcer?

A
  • Reduce acid secretion with H2 receptor antagonists
  • Neutralise secreted acid with antacids
  • Attempt to eradicate H.pylori
17
Q

What is the function of Antacids?

A

Neutralise gastric acid and increase pH

form a raft on top of acidic chyme which reduces amount of acidic chyme that refluxes into and damages oesophagus

18
Q

What is the role of Bismuth chelate?

A

Absorbs pepsin (stops it from working) and increases HCO3- and PG secretion, protecting the gastric mucosa

also is toxic against H.pylori

19
Q

What is the Bismuth chelate effect on stool and tongue?

A

Blackens stool and tongue

20
Q

What is the Caution of bismuth chelate?

A

If patient has renal impairment, concentration of bismuth chelate in blood will rise and can cause encephalopathy

21
Q

Why do NSAIDs (e.g. aspirin) cause gastric bleeding?

A

Because they inhibit PG synthesis (less protection) and Thromboxane A2 (involved in healing)

COX-2 inhibitors are more stomach friendly and cause less bleeding (e.g. Celecoxib and Rofecoxib)

22
Q

Describe Combination therapy against H.pylori.

A
  • Omeprazole, amoxicillin, metronidazole
  • Omeprazole, clarythromycin and amoxicillin or tetracycline, metronidazole and bismuth chelates
  • Lansoprazole, clarithromycin, tinidazole and bismuth chelates

They also cannot drink alcohol if they take metronidazole as it results in disulfiram like reaction, the patient will feel severely ill and may stop taking the drug.
-> Disulfiram inhibits aldehyde dehydrogenase causing a build-up of acetaldehyde, resulting in unpleasant flushing and nausea.

Also, do not give in the first trimester as it will affect the foetus and cause birth defects

23
Q

What is Constipation?

A

Increased water loss from faeces leading to drier faeces, making it more painful and harder to defecate

24
Q

Give some Causes of constipation.

A

Decreased motility of large intestine due to:

  • old age
  • damage to ENS
25
Q

Give some Factors that increase colonic motility.

A

Increased fibre, cellulose and complex polysaccharides

Laxatives (but excessive use will decrease responsiveness to them)

Mineral oil (lubricates faeces)

Castor oil (stimulates motility of colon)

26
Q

Name some Drugs to manage constipation.

A

Purgatives

Bulk forming laxatives

Osmotic laxatives (lactulose)

27
Q

What is Diarrhoea?

A

Frequent passage of liquid faeces

28
Q

What is Loperamide and Codeine?

A

Antidiarrhoeal agent which decreases intestinal motility and decreases passage of faeces and decreases duration of illness

29
Q

What is the function of bismuth subsalicylate (chelate)?

A

Decreases fluid secretion in bowel

30
Q

How does loperamide work?

A

u-opioid receptor agonist of the myenteric plexus of large intestine

reduces smooth muscle activity in the GIT, reducing force of colonic movement and thus reduces passage of faeces

increases haustral mixing of proximal colon and inhibits propulsive mass movement of the distal colon

does not cross blood brain barrier therefore has no CNS effects

inhibits gastric emptying, increases sphincter tone, induces stationary motor patterns and blocks peristalsis

GI System (15 decks)

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